The overall goal of this project is to assess systemic delivery of angiostatic genes as a means of inhibiting tumor antiogenesis. The specific objectives are to compare two methods of systemic gene delivery and two angiostatic genes for their ability to inhibit angiogenesis and tumor growth, using both experimental tumor models (mice) and hypothesis that sustained systemic production of an angiostatic factor by in vivo gene delivery can inhibit angiogenesis in animals with established tumors. The rationale for this proposal is that sustained in vivo expression of angiostatic genes by systemic non-viral gene delivery techniques may be a more effective and practical approach to angiogenesis inhibition than repeated parenteral injections of purified proteins. Two endogenous angiostatic factors (endostatin and angiostatin), that have both demonstrated impressive antitumor activity in vivo, will be evaluated. The objective of this proposal will be accomplished using three specific aims: (1) compare the effectiveness of intravenous versus intramuscular gene delivery in murine tumor models; (2) determine optimal DNA doses for intravenous and intramuscular gene delivery in dogs; and (3) assess antiangiogenic activity and tumor responses to systemic endostatin gene therapy in dogs with malignant melanoma. The results of these studies, which include assessment of angiogenic markers and treatment outcomes in a pertinent large animal tumor model, will provide a clinically realistic evaluation of this novel approach to inhibition to tumor angiogenesis. Such an approach may be broadly applicable to therapeutic modulation of aniogenesis in general, using genes or combinations of genes that either inhibit or stimulate angiogenesis.